The invention relates to communication networks in general and more particularly to a protocol for stripping data from a token ring network using both early token release and a multi-frame transmit mode.
The above-referenced related application discusses the concepts of normal and early token release and is incorporated herein by reference. In early token release, a transmitting station can release the token as soon as it completes frame transmission, thus making the token available to other stations waiting to transmit sooner than in normal token release. The co-pending application addresses the situation where a station on the ring transmits a token immediately after sending one frame of data. Although multiple frames can be on the ring simultaneously, only one frame can be placed on the ring by a given station. The disclosed method for removing corrupted messages involves a check for two conditions and the occurrence of either terminates frame stripping at a receiving station. In the first test, the receiving station compares the source address of the received frame against the source address of the frame that is transmitted. If they do not match and no code violation errors are detected within the frame header, the receiving station stops its stripping operation immediately. The second condition disclosed for terminating the stripping operation of a receiving station is the detection of an isolated ending delimiter, i.e., an ending delimiter that was not preceded by a paired starting delimiter.
In certain special application token ring networks, there is a requirement to have a single station transmit multiple frames onto the ring before releasing the token to enable other stations to transmit. Typical situations are an air traffic control network or the flight arrival and departure network at airports where there is a requirement for real-time updates and the transmissions are numerous, short and bursty in nature. Rapid recovery of the token ring network in these environments is critical. However, the disclosed process in the related application for recognizing corrupted frames and terminating the strip operation will not be effective in a multi-frame transmit situation (multiple frames being transmitted by one station). Furthermore, neither the IEEE 802.5 protocol standard for token rings nor the proposed American National Standards Institute (ANSI) standard X3T9.5 for Fiber Distributed Data Interface (FDDI) address the problems solved by this invention.